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6搜索和解码黎塔lita@hccl.ioa.ac.cn语言声学与内容理解重点实验室中国科学院声学研究所2014-04-10提纲概述搜索空间知识源搜索空间构建搜索空间优化解码和词图生成解码算法词图基于WFST语音识别多遍融合解码系统6.1概述语音识别问题模式识别语言模型声学模型发音字典特征搜索问题(解码)给定模型找到与特征相匹配文本6.1概述解码技术快速准确6.1概述whatwasW?knowingO,priorknowledgesource:languagemodel(LM):P(W)(oftenM-gram;)dictionary:words=triphone(W=Ph)acousticmodel:p(O|PH),HMMslanguagegenerationpronunciationspeechproductionwordsequenceW=(w1...wN)sequenceoftriphonePH=(ph1...phN)soundwavestransmissionSRfront-endprocessingobservationvectorsO=(o1...oT)?LM:P(W)dictio-nary}AM:p(O|S)6.1概述贝叶斯框架及viterbi近似6.1概述提纲概述搜索空间知识源搜索空间构建搜索空间优化解码和词图生成解码算法词图基于WFST语音识别多遍融合解码系统6.2搜索空间什么是搜索空间文本搜索InformationRetrieval多媒体检索什么是语音识别的搜索空间语音识别知识源空间完备精简6.2.1知识源语言模型发音字典声学上下文声学模型特征6.2.1知识源语言模型词图/有限状态图N元统计语言模型),|(),,|(21121NNNNNN6.2.1知识源发音字典声学上下文声学模型隐含马尔科夫模型(HMM)特征MFCC,PLP,LPCC….6.2.2搜索空间构建发音字典(线性)6.2.2搜索空间构建发音字典(前缀树)6.2.2搜索空间构建15sihaetdsittsatsadrootNextword6.2.2搜索空间构建6.2.2搜索空间构建WithinWord和CrossWord6.2.2搜索空间构建孤立词识别固定识别词边界6.2.2搜索空间构建受限词图识别6.2.2搜索空间构建大词表连续语音识别(LVCSR)特点大词汇连续语音语言模型延迟难点搜索空间占用内存大搜索速度慢6.2.2搜索空间构建LVCSR搜索空间-Unigram6.2.2搜索空间构建LVCSR搜索空间-Bigram6.2.2搜索空间构建LVCSR搜索空间-backoff6.2.2搜索空间构建对句中的静音处理6.2.3搜索空间的优化优化准则不改变空间完备性减少重复路径知识源信息紧耦合目标减少搜索空间内存提高搜索速度6.2.3搜索空间的优化前向后向归并搜索算法3forwardmergebackwardmerge456σσss1278349σσs1278109σs12786.2.3搜索空间的优化-example例子:受限词图6.2.3搜索空间的优化-example原始词图6.2.3搜索空间的优化-exampleWordgraph-》phonemenetwork6.2.3搜索空间的优化-exampleTriphonenetwork搜索空间构建优化的网络6.2.3搜索空间的优化LVCSR搜索空间动态动态加载知识源解码过程需要查询知识源信息内存占用小,空间构建速度快解码速度不够快静态预先编译好知识源解码过程就是一个FST的搜索问题内存占用大,空间构建速度慢解码速度快6.2.3搜索空间的优化LVCSR搜索空间动态词典树6.2.3搜索空间的优化LVCSR搜索空间静态WFST(G·L)6.2.3搜索空间的优化北极(north-pole)b-ei3-j-i2北京(Beijing)b-ei3-j-ing1南京(Nanjing)n-an2-j-jing1!SENT_PAUSEsil!SENT_ENDsil!SEND_STARTsil三词线性词典ing1-b+ei3词头三音子声学上下文:词内三音子词尾三音子b-ei3+jj-ing1+n初始网络构造Howtoreduceredundancy?8769079422298231623252298232023367北极spwespwe60InitialMid-partFinalFIFOWIWE816ROOT10171819202122232425261662365236951647165412345687690794233北京123413141516623651369816471654272829303132324432593264324932623266spwespwe3536373839404142434451南京529543367451845464748495040104059408652535455400940594086565758593728373136983731911ing1-b+ei3b-ei3+jei3-j+i2i2-b+ei3ing1-n+an2i2-n+an2n-an2+jan2-j+ing1ing1-bj-i2+bj-i2+nj-ing1+bj-ing1+nb-ei3+ji2-bing1-ni2-nj-i2j-ing1ei3-j+ing1SPAWDW876907942S1S2S3ing1-b+ei3三音子状态ID音素决策树映射6.2.3搜索空间的优化LVCSR搜索空间前后向归并8769079422298231623252298232023367北极spwespwe60InitialMid-partFinalFIFOWIWE816ROOT10171819202122232425261662365236951647165412345687690794233北京123413141516623651369816471654272829303132324432593264324932623266spwespwe3536373839404142434451南京529543367451845464748495040104059408652535455400940594086565758593728373136983731911ing1-b+ei3b-ei3+jei3-j+i2i2-b+ei3ing1-n+an2i2-n+an2n-an2+jan2-j+ing1ing1-bj-i2+bj-i2+nj-ing1+bj-ing1+nb-ei3+ji2-bing1-ni2-nj-i2j-ing1ei3-j+ing1SPAWDW231623252298232023367北极spwespwe60InitialMid-partFinalFIFOWE816ROOT1819202164232425263652369545687690794233北京12346766651662365116471654616263306968324432593264324932623266spwespwe35363738394041424344南京5295433674518454647484010408652534009405956577170372836983731ing1-b+ei3b-ei3+jei3-j+i2i2-b+ei3ing1-n+an2i2-n+an2n-an2+jan2-j+ing1ing1-bj-i2+bj-i2+nj-ing1+bj-ing1+nei3-j+ing1i2-bing1-ni2-nj-i2j-ing151WIAWSPDW6.2.3搜索空间的优化LVCSR搜索空间37WI节点提前更有效进行前后向归并算法解码尽快加入语言模型信息8769079422298231623252298232023367北极spwespwe60InitialMid-partFinalFIFOWIWE816ROOT10171819202122232425261662365236951647165412345687690794233北京123413141516623651369816471654272829303132324432593264324932623266spwespwe3536373839404142434451南京529543367451845464748495040104059408652535455400940594086565758593728373136983731911ing1-b+ei3b-ei3+jei3-j+i2i2-b+ei3ing1-n+an2i2-n+an2n-an2+jan2-j+ing1ing1-bj-i2+bj-i2+nj-ing1+bj-ing1+nb-ei3+ji2-bing1-ni2-nj-i2j-ing1ei3-j+ing1SPAWDW231623252298232023367北极spwespwe60InitialMid-partFinalFIFOWE816ROOT1819202164232425263652369545687690794233北京12346766651662365116471654616263306968324432593264324932623266spwespwe35363738394041424344南京5295433674518454647484010408652534009405956577170372836983731ing1-b+ei3b-ei3+jei3-j+i2i2-b+ei3ing1-n+an2i2-n+an2n-an2+jan2-j+ing1ing1-bj-i2+bj-i2+nj-ing1+bj-ing1+nei3-j+ing1i2-bing1-ni2-nj-i2j-ing151WIAWSPDW6.2.3搜索空间的优化231623252298232023367北极spwespwe60InitialMid-partFinalFIFOWE816ROOT1819202164232425263652369545687690794233北京12346766651662365116471654616263306968324432593264324932623266spwespwe35363738394041424344南京5295433674518454647484010408652534009405956577170372836983731ing1-b+ei3b-ei3+jei3-j+i2i2-b+ei3ing1-n+an2i2-n+an2n-an2+jan2-j+ing1ing1-bj-i2+bj-i2+nj-ing1+bj-ing1+nei3-j+ing1i2-bing1-ni2-nj-i2j-ing151WIAWSPDWFI(fan-in)WE(wordend)WI(wordid)AW(aboveWI)DW(downWI)解码空间分层路径管理结构清晰独立剪枝集成语言模型提纲概述搜索空间知识源搜索空间构建搜索空间优化解码和词图生成解码算法词图基于WFST语音识别多遍融合解码系统6.3解码和词图生成解码算法快速搜索空间中找到最可能路径词图识别中间结果信息丰富6.3.1解码算法动态规划(DynamicProgramming)6.3.1解码算法动态时间规整(DTW)6.3.1解码算法基本图搜索算法6.3.1解码算法树搜索空间6.3.1解码算法深度优先搜索(Depthfirst)6.3.1解码算法宽度优先搜索(Breadthfirst)6.3.1解码算法时间
本文标题:语音识别解码
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